This invention relates to apparatus for the feeding of printed sheets and, more particularly, to a proximity caliper for detecting the thickness of printed signatures.
Devices for feeding printed signatures having two or more pages are employed for accumulating several different signatures to form a book or magazine. An example of such a device is shown in U.S. Pat. No. 3,880,419. This structure is capable of feeding printed signatures of different dimensions and thicknesses.
The apparatus shown in the above-cited patent is not equipped with means for sensing the correct thickness of the individual signatures which are fed from a stack supply to a conveyor by way of a rotatable drum. The thickness of the signature is proportional to the number of pages in it and thus, if a page is missing or if an extra page is included, this undesirable condition is not detected.
I have invented a device capable of being mounted on an apparatus for feeding printed sheets including the apparatus of the type shown in the above-cited patent which, after being appropriately adjusted, senses the thickness of the printed signature being fed.